Atmospheric Mercury in Milan Area (Italy)
Mercury is a very hazardous substance for human health and the environment, and the atmosphere is the major pathway of transport from emission sources to receptors.
In order to assess concentration levels of mercury in Milan area, monthly monitoring campaigns for total gaseous mercury (TGM) in ambient air have been performed in the last two years at a downtown site and 4 suburban sites, close to Milan’s waste incinerator plant.
TGM concentrations were measured by means of an automated instrument based on Atomic Absorption Spectrometry (Mercury Ultratracer UT-3000) with a resolution of about 0.2 ng m-3. Ambient air is sampled at a flowrate of 4 liters per hour, filtered by a 0.45 µm PTFE and then pulled through a gold trap where mercury is captured; trapped mercury is then released as a gas by thermal desorption and swept by a flow of purified air into the optical cell of the detector.
The full database contains hourly concentration data for 10 24-hr campaigns for each site. Daily concentration levels are below 10 ng m-3, with slightly higher values in the cold seasons. Inter-site comparison of concentration data is performed in order to point out differences between urban and suburban locations, while intra-site comparisons are used to evidence seasonality effects. Moreover, the role of meteorological conditions is analysed by comparing the daily patterns of TGM concentrations to those of the main meteorological parameters and particularly to the mixing layer height.